bg-image($url)
    background-image url($url + "@2x.png")
    @media (-webkit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3)
        background-image url($url + "@3x.png")

border-1px($color)
  position relative
  &:after
    display block
    position absolute
    left 0
    bottom 0
    width 100%
    border-top 1px solid $color
    transform scaleY(0.5)
    transform-origin 0 100%
    content: ''
